diff --git a/blob.c b/blob.c
index 337e3333..a8f28c9b 100644
--- a/blob.c
+++ b/blob.c
@@ -64,7 +64,7 @@ pic_blob_bytevector(pic_state *pic)
     pic_assert_type(pic, argv[i], int);
 
     if (pic_int(argv[i]) < 0 || pic_int(argv[i]) > 255) {
-      pic_error(pic, "byte out of range");
+      pic_errorf(pic, "byte out of range");
     }
 
     *data++ = pic_int(argv[i]);
@@ -82,7 +82,7 @@ pic_blob_make_bytevector(pic_state *pic)
   pic_get_args(pic, "i|i", &k, &b);
 
   if (b < 0 || b > 255)
-    pic_error(pic, "byte out of range");
+    pic_errorf(pic, "byte out of range");
 
   blob = pic_make_blob(pic, k);
   for (i = 0; i < k; ++i) {
@@ -122,7 +122,7 @@ pic_blob_bytevector_u8_set(pic_state *pic)
   pic_get_args(pic, "bii", &bv, &k, &v);
 
   if (v < 0 || v > 255)
-    pic_error(pic, "byte out of range");
+    pic_errorf(pic, "byte out of range");
 
   bv->data[k] = v;
   return pic_none_value();
@@ -227,7 +227,7 @@ pic_blob_list_to_bytevector(pic_state *pic)
     pic_assert_type(pic, e, int);
 
     if (pic_int(e) < 0 || pic_int(e) > 255)
-      pic_error(pic, "byte out of range");
+      pic_errorf(pic, "byte out of range");
 
     *data++ = pic_int(e);
   }
diff --git a/char.c b/char.c
index 0dca9f52..a460fb2b 100644
--- a/char.c
+++ b/char.c
@@ -53,7 +53,7 @@ pic_char_integer_to_char(pic_state *pic)
       if (pic_char_p(argv[i]))                          \
         d = pic_char(argv[i]);                          \
       else						\
-	pic_error(pic, #op ": char required");          \
+	pic_errorf(pic, #op ": char required");         \
       							\
       if (! (c op d))					\
 	return pic_false_value();			\
diff --git a/codegen.c b/codegen.c
index 34505723..55bb8587 100644
--- a/codegen.c
+++ b/codegen.c
@@ -425,7 +425,7 @@ analyze_lambda(analyze_state *state, pic_value obj)
   pic_value formals, body_exprs;
 
   if (pic_length(pic, obj) < 2) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   formals = pic_list_ref(pic, obj, 1);
@@ -450,12 +450,12 @@ analyze_define(analyze_state *state, pic_value obj)
   pic_sym sym;
 
   if (pic_length(pic, obj) != 3) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   var = pic_list_ref(pic, obj, 1);
   if (! pic_sym_p(var)) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   } else {
     sym = pic_sym(var);
   }
@@ -472,7 +472,7 @@ analyze_define(analyze_state *state, pic_value obj)
     val = analyze_defer(state, pic_sym_value(sym), formals, body_exprs);
   } else {
     if (pic_length(pic, obj) != 3) {
-      pic_error(pic, "syntax error");
+      pic_errorf(pic, "syntax error");
     }
     val = analyze(state, pic_list_ref(pic, obj, 2), false);
   }
@@ -489,7 +489,7 @@ analyze_if(analyze_state *state, pic_value obj, bool tailpos)
   if_false = pic_none_value();
   switch (pic_length(pic, obj)) {
   default:
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
     break;
   case 4:
     if_false = pic_list_ref(pic, obj, 3);
@@ -539,12 +539,12 @@ analyze_set(analyze_state *state, pic_value obj)
   pic_value var, val;
 
   if (pic_length(pic, obj) != 3) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   var = pic_list_ref(pic, obj, 1);
   if (! pic_sym_p(var)) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   val = pic_list_ref(pic, obj, 2);
@@ -561,14 +561,14 @@ analyze_quote(analyze_state *state, pic_value obj)
   pic_state *pic = state->pic;
 
   if (pic_length(pic, obj) != 2) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
   return pic_list2(pic, pic_sym_value(pic->sQUOTE), pic_list_ref(pic, obj, 1));
 }
 
 #define ARGC_ASSERT_GE(n) do {				\
 	if (pic_length(pic, obj) < (n) + 1) {		\
-	  pic_error(pic, "wrong number of arguments");	\
+	  pic_errorf(pic, "wrong number of arguments");	\
 	}						\
       } while (0)
 
@@ -699,7 +699,7 @@ analyze_call_with_values(analyze_state *state, pic_value obj, bool tailpos)
   pic_sym call;
 
   if (pic_length(pic, obj) != 3) {
-    pic_error(pic, "wrong number of arguments");
+    pic_errorf(pic, "wrong number of arguments");
   }
 
   if (! tailpos) {
@@ -714,7 +714,7 @@ analyze_call_with_values(analyze_state *state, pic_value obj, bool tailpos)
 
 #define ARGC_ASSERT(n) do {				\
 	if (pic_length(pic, obj) != (n) + 1) {		\
-	  pic_error(pic, "wrong number of arguments");	\
+	  pic_errorf(pic, "wrong number of arguments");	\
 	}						\
       } while (0)
 
@@ -1413,7 +1413,7 @@ codegen(codegen_state *state, pic_value obj)
     cxt->clen++;
     return;
   }
-  pic_error(pic, "codegen: unknown AST type");
+  pic_errorf(pic, "codegen: unknown AST type");
 }
 
 static struct pic_irep *
diff --git a/include/picrin.h b/include/picrin.h
index e726ee4c..e911ff04 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -209,10 +209,6 @@ pic_str *pic_get_backtrace(pic_state *);
 void pic_print_backtrace(pic_state *, struct pic_error *);
 
 /* obsoleted */
-noreturn static inline void pic_error(pic_state *pic, const char *msg)
-{
-  pic_errorf(pic, msg);
-}
 static inline void pic_warn(pic_state *pic, const char *msg)
 {
   pic_warnf(pic, msg);
diff --git a/macro.c b/macro.c
index 17f12cc6..c7cd243f 100644
--- a/macro.c
+++ b/macro.c
@@ -161,7 +161,7 @@ macroexpand_lambda(pic_state *pic, pic_value expr, struct pic_senv *senv)
   pic_value a;
 
   if (pic_length(pic, expr) < 2) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   in = pic_make_senv(pic, senv);
@@ -170,7 +170,7 @@ macroexpand_lambda(pic_state *pic, pic_value expr, struct pic_senv *senv)
     pic_value v = pic_car(pic, a);
 
     if (! pic_sym_p(v)) {
-      pic_error(pic, "syntax error");
+      pic_errorf(pic, "syntax error");
     }
     pic_add_rename(pic, in, pic_sym(v));
   }
@@ -178,7 +178,7 @@ macroexpand_lambda(pic_state *pic, pic_value expr, struct pic_senv *senv)
     pic_add_rename(pic, in, pic_sym(a));
   }
   else if (! pic_nil_p(a)) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   formal = macroexpand_list(pic, pic_cadr(pic, expr), in);
@@ -203,12 +203,12 @@ macroexpand_define(pic_state *pic, pic_value expr, struct pic_senv *senv)
   }
 
   if (pic_length(pic, expr) != 3) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   var = pic_cadr(pic, expr);
   if (! pic_sym_p(var)) {
-    pic_error(pic, "binding to non-symbol object");
+    pic_errorf(pic, "binding to non-symbol object");
   }
   sym = pic_sym(var);
   if (! pic_find_rename(pic, senv, sym, &rename)) {
@@ -226,12 +226,12 @@ macroexpand_defsyntax(pic_state *pic, pic_value expr, struct pic_senv *senv)
   pic_sym sym, rename;
 
   if (pic_length(pic, expr) != 3) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   var = pic_cadr(pic, expr);
   if (! pic_sym_p(var)) {
-    pic_error(pic, "binding to non-symbol object");
+    pic_errorf(pic, "binding to non-symbol object");
   }
   sym = pic_sym(var);
   if (! pic_find_rename(pic, senv, sym, &rename)) {
diff --git a/number.c b/number.c
index 10dc03aa..4c13df35 100644
--- a/number.c
+++ b/number.c
@@ -179,7 +179,7 @@ pic_number_nan_p(pic_state *pic)
       else if (pic_int_p(argv[i]))			\
 	g = pic_int(argv[i]);				\
       else						\
-	pic_error(pic, #op ": number required");	\
+	pic_errorf(pic, #op ": number required");	\
       							\
       if (! (f op g))					\
 	return pic_false_value();			\
@@ -216,7 +216,7 @@ DEFINE_ARITH_CMP(>=, ge)
         f op##= pic_float(argv[i]);                             \
       }                                                         \
       else {                                                    \
-        pic_error(pic, #op ": number required");                \
+        pic_errorf(pic, #op ": number required");               \
       }                                                         \
     }                                                           \
                                                                 \
@@ -252,7 +252,7 @@ DEFINE_ARITH_OP(*, mul, 1)
        f op##= pic_float(argv[i]);                                      \
      }                                                                  \
      else {                                                             \
-       pic_error(pic, #op ": number required");                         \
+       pic_errorf(pic, #op ": number required");                        \
      }                                                                  \
    }                                                                    \
                                                                         \
diff --git a/pair.c b/pair.c
index d9960347..0bb0d90e 100644
--- a/pair.c
+++ b/pair.c
@@ -51,7 +51,7 @@ pic_set_car(pic_state *pic, pic_value obj, pic_value val)
   struct pic_pair *pair;
 
   if (! pic_pair_p(obj)) {
-    pic_error(pic, "pair required");
+    pic_errorf(pic, "pair required");
   }
   pair = pic_pair_ptr(obj);
 
@@ -64,7 +64,7 @@ pic_set_cdr(pic_state *pic, pic_value obj, pic_value val)
   struct pic_pair *pair;
 
   if (! pic_pair_p(obj)) {
-    pic_error(pic, "pair required");
+    pic_errorf(pic, "pair required");
   }
   pair = pic_pair_ptr(obj);
 
@@ -520,7 +520,7 @@ pic_pair_set_car(pic_state *pic)
   pic_get_args(pic, "oo", &v, &w);
 
   if (! pic_pair_p(v))
-    pic_error(pic, "pair expected");
+    pic_errorf(pic, "pair expected");
 
   pic_pair_ptr(v)->car = w;
   return pic_none_value();
@@ -534,7 +534,7 @@ pic_pair_set_cdr(pic_state *pic)
   pic_get_args(pic, "oo", &v, &w);
 
   if (! pic_pair_p(v))
-    pic_error(pic, "pair expected");
+    pic_errorf(pic, "pair expected");
 
   pic_pair_ptr(v)->cdr = w;
   return pic_none_value();
diff --git a/port.c b/port.c
index 859df8a5..558a81b6 100644
--- a/port.c
+++ b/port.c
@@ -107,7 +107,7 @@ void
 pic_close_port(pic_state *pic, struct pic_port *port)
 {
   if (xfclose(port->file) == EOF) {
-    pic_error(pic, "close-port: failure");
+    pic_errorf(pic, "close-port: failure");
   }
   port->status = PIC_PORT_CLOSE;
 }
@@ -247,25 +247,25 @@ pic_port_close_port(pic_state *pic)
     if ((port->flags & (flgs)) != (flgs)) {                             \
       switch (flgs) {                                                   \
       case PIC_PORT_IN:                                                 \
-        pic_error(pic, caller ": expected output port");                \
+        pic_errorf(pic, caller ": expected output port");               \
       case PIC_PORT_OUT:                                                \
-        pic_error(pic, caller ": expected input port");                 \
+        pic_errorf(pic, caller ": expected input port");                \
       case PIC_PORT_IN | PIC_PORT_TEXT:                                 \
-        pic_error(pic, caller ": expected input/textual port");         \
+        pic_errorf(pic, caller ": expected input/textual port");        \
       case PIC_PORT_IN | PIC_PORT_BINARY:                               \
-        pic_error(pic, caller ": expected input/binary port");          \
+        pic_errorf(pic, caller ": expected input/binary port");         \
       case PIC_PORT_OUT | PIC_PORT_TEXT:                                \
-        pic_error(pic, caller ": expected output/textual port");        \
+        pic_errorf(pic, caller ": expected output/textual port");       \
       case PIC_PORT_OUT | PIC_PORT_BINARY:                              \
-        pic_error(pic, caller ": expected output/binary port");         \
+        pic_errorf(pic, caller ": expected output/binary port");        \
       }                                                                 \
     }                                                                   \
     if (port->status != stat) {                                         \
       switch (stat) {                                                   \
       case PIC_PORT_OPEN:                                               \
-        pic_error(pic, caller ": expected open port");                  \
+        pic_errorf(pic, caller ": expected open port");                 \
       case PIC_PORT_CLOSE:                                              \
-        pic_error(pic, caller ": expected close port");                 \
+        pic_errorf(pic, caller ": expected close port");                \
       }                                                                 \
     }                                                                   \
   } while (0)
diff --git a/proc.c b/proc.c
index 1dee4813..9702819c 100644
--- a/proc.c
+++ b/proc.c
@@ -91,7 +91,7 @@ pic_proc_apply(pic_state *pic)
   pic_get_args(pic, "l*", &proc, &argc, &args);
 
   if (argc == 0) {
-    pic_error(pic, "apply: wrong number of arguments");
+    pic_errorf(pic, "apply: wrong number of arguments");
   }
 
   arg_list = args[--argc];
diff --git a/string.c b/string.c
index fc2d2ab6..6876a969 100644
--- a/string.c
+++ b/string.c
@@ -404,7 +404,7 @@ pic_str_string_append(pic_state *pic)
   str = pic_make_str(pic, NULL, 0);
   for (i = 0; i < argc; ++i) {
     if (! pic_str_p(argv[i])) {
-      pic_error(pic, "type error");
+      pic_errorf(pic, "type error");
     }
     str = pic_strcat(pic, str, pic_str_ptr(argv[i]));
   }
diff --git a/symbol.c b/symbol.c
index 7c6479b4..6629abac 100644
--- a/symbol.c
+++ b/symbol.c
@@ -132,7 +132,7 @@ pic_symbol_symbol_to_string(pic_state *pic)
   pic_get_args(pic, "o", &v);
 
   if (! pic_sym_p(v)) {
-    pic_error(pic, "symbol->string: expected symbol");
+    pic_errorf(pic, "symbol->string: expected symbol");
   }
 
   return pic_obj_value(pic_make_str_cstr(pic, pic_symbol_name(pic, pic_sym(v))));
@@ -146,7 +146,7 @@ pic_symbol_string_to_symbol(pic_state *pic)
   pic_get_args(pic, "o", &v);
 
   if (! pic_str_p(v)) {
-    pic_error(pic, "string->symbol: expected string");
+    pic_errorf(pic, "string->symbol: expected string");
   }
 
   return pic_symbol_value(pic_intern_cstr(pic, pic_str_cstr(pic_str_ptr(v))));
diff --git a/vector.c b/vector.c
index 4a3e8194..57790b36 100644
--- a/vector.c
+++ b/vector.c
@@ -105,7 +105,7 @@ pic_vec_vector_ref(pic_state *pic)
   pic_get_args(pic, "vi", &v, &k);
 
   if (k < 0 || v->len <= (size_t)k) {
-    pic_error(pic, "vector-ref: index out of range");
+    pic_errorf(pic, "vector-ref: index out of range");
   }
   return v->data[k];
 }
@@ -120,7 +120,7 @@ pic_vec_vector_set(pic_state *pic)
   pic_get_args(pic, "vio", &v, &k, &o);
 
   if (k < 0 || v->len <= (size_t)k) {
-    pic_error(pic, "vector-set!: index out of range");
+    pic_errorf(pic, "vector-set!: index out of range");
   }
   v->data[k] = o;
   return pic_none_value();
diff --git a/vm.c b/vm.c
index b84bc96e..609c702f 100644
--- a/vm.c
+++ b/vm.c
@@ -29,7 +29,7 @@ pic_get_proc(pic_state *pic)
   pic_value v = GET_OPERAND(pic,0);
 
   if (! pic_proc_p(v)) {
-    pic_error(pic, "fatal error");
+    pic_errorf(pic, "fatal error");
   }
   return pic_proc_ptr(v);
 }
@@ -70,7 +70,7 @@ pic_get_args(pic_state *pic, const char *format, ...)
     switch (c) {
     default:
       if (argc <= i && ! opt) {
-	pic_error(pic, "wrong number of arguments");
+	pic_errorf(pic, "wrong number of arguments");
       }
       break;
     case '|':
@@ -375,7 +375,7 @@ pic_get_args(pic_state *pic, const char *format, ...)
           *e = pic_error_ptr(v);
         }
         else {
-          pic_error(pic, "pic_get_args, expected error");
+          pic_errorf(pic, "pic_get_args, expected error");
         }
         i++;
       }
@@ -398,7 +398,7 @@ pic_get_args(pic_state *pic, const char *format, ...)
     }
   }
   else if (argc > i) {
-    pic_error(pic, "wrong number of arguments");
+    pic_errorf(pic, "wrong number of arguments");
   }
   va_end(ap);
   return i - 1;
@@ -675,7 +675,7 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
 #endif
 
   if (! pic_list_p(argv)) {
-    pic_error(pic, "argv must be a proper list");
+    pic_errorf(pic, "argv must be a proper list");
   }
 
   argc = pic_length(pic, argv) + 1;
@@ -728,11 +728,11 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
 
       self = pic->ci->fp[0];
       if (! pic_proc_p(self)) {
-        pic_error(pic, "logic flaw");
+        pic_errorf(pic, "logic flaw");
       }
       irep = pic_proc_ptr(self)->u.irep;
       if (! pic_proc_irep_p(pic_proc_ptr(self))) {
-        pic_error(pic, "logic flaw");
+        pic_errorf(pic, "logic flaw");
       }
       PUSH(irep->pool[c.u.i]);
       NEXT;
@@ -950,11 +950,11 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
 
       self = pic->ci->fp[0];
       if (! pic_proc_p(self)) {
-        pic_error(pic, "logic flaw");
+        pic_errorf(pic, "logic flaw");
       }
       irep = pic_proc_ptr(self)->u.irep;
       if (! pic_proc_irep_p(pic_proc_ptr(self))) {
-        pic_error(pic, "logic flaw");
+        pic_errorf(pic, "logic flaw");
       }
 
       if (pic->ci->env == NULL) {
@@ -1017,7 +1017,7 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
 	PUSH(pic_float_value(pic_float(a) op pic_int(b)));	\
       }								\
       else {							\
-	pic_error(pic, #op " got non-number operands");		\
+	pic_errorf(pic, #op " got non-number operands");        \
       }								\
       NEXT;							\
     }
@@ -1037,7 +1037,7 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
 	PUSH(pic_float_value(-pic_float(n)));
       }
       else {
-	pic_error(pic, "unary - got a non-number operand");
+	pic_errorf(pic, "unary - got a non-number operand");
       }
       NEXT;
     }
@@ -1060,7 +1060,7 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
 	PUSH(pic_bool_value(pic_float(a) op pic_int(b)));	\
       }								\
       else {							\
-	pic_error(pic, #op " got non-number operands");		\
+	pic_errorf(pic, #op " got non-number operands");        \
       }								\
       NEXT;							\
     }